Chemical Science Blog

US scientists have reported the preparation and synthetic applications of sulfinimines derived from benzoquinone monoketals. The method provides the first direct access to a variety of enantioenriched 4-aminocyclohexadienones, which possess synthetic handles for further elaboration to alkaloid natural products, say the researchers.

They demonstrated the the utility of the method in a short, enantioselective total synthesis of the natural product 3-demethoxyerythratidinone.

Read more:
Benzoquinone-derived sulfinyl imines as versatile intermediates for alkaloid synthesis: Total synthesis of (–)-3-demethoxyerythratidinone
K V Chuang, R Navarro and S E Reisman, Chem. Sci., 2011, DOI: 10.1039/c1sc00095k

UK scientists have come up with a new design rule for organic photovoltaics (OPVs), which could lead to improved solar cells.

Until recently, many of the polymers studied for OPVs had originally been developed for the more mature organic light emitting diode (OLED) and organic field effect transistor fields. For OLEDs, a high photoluminescence (PL) emission yield is a prerequisite, and this was also thought to be a positive indicator of a polymer’s OPV suitability.

But, by comparing the photophysics and photovoltaic performance of two different polymer–fullerene blends, James Durrant and colleagues have demonstrated that a high PL yield is not necessarily a positive attribute for polymers for OPV. OPV polymers should not, in general, exhibit strong photoluminescence which spectrally overlaps with fullerene absorption.

Read Energy versus electron transfer in organic solar cells: a comparison of the photophysics of two indenofluorene: fullerene blend films for free today to find out more.

A water molecule can act as a spy to sense and expose the reasons behind the anomeric effect in carbohydrates.

Since it was identified more than 50 years ago, the anomeric effect’s origins have been hotly debated. Scientists have found it difficult to separate stereoelectronic effects from other potential influences, including solvation.

Using vibrational spectroscopy, researchers have studied doubly hydrated anomers of a mannopyranoside under molecular beam conditions in the gas phase. By substituting heavy water (D₂O) for H₂O, they separated the carbohydrate (OH) bands from the water (OD) bands, helping them to interpret differences in the anomers’ vibrational signatures. One of the water molecules acted as a remarkably sensitive reporter, able to sense and expose subtle stereoelectronic changes through the resulting changes in its hydrogen-bonded interaction with the substrate.

Eager to read more? Download the full Edge article in Chemical Science for free:
Heavy water hydration of mannose: the anomeric effect in solvation, laid bare
Nitzan Mayorkas, Svemir Rudić, Benjamin G. Davis and John P. Simons, Chem. Sci., 2011, DOI: 10.1039/C1SC00002K

Scientists in Germany have developed a strategy to visualise oxygen concentrations in cells to better understand its role in biological reactions such as metabolism.

Hans Gorris from the University of Regensburg and colleagues have embedded two luminescent dyes within polystyrene particles, which were taken up by cells. One is a red light-emitting indicator dye that alters its luminescence depending on the oxygen concentration; the second is a green light-emitting dye that acts as a reference and is not sensitive to oxygen. The colours enabled the dyes to be monitored on the green and red channels in a red-green-blue (RGB) digital camera, together with a fluorescence microscope.

Schematic drawing of a ratiometric oxygen-sensitive polystyrene PEBBLE

See Chemistry World for the full news story  

Link to journal article
Self-referenced RGB colour imaging of intracellular oxygen
Xu-dong Wang, Hans H. Gorris, Judith A. Stolwijk, Robert J. Meier, Dominik B. M. Groegel, Joachim Wegener and Otto S. Wolfbeis
Chem. Sci., 2011, DOI: 10.1039/c0sc00610f

amyloid fibrils

Group 9 metal complexes can inhibit amyloid aggregation, thought to be responsible for neurodegeneration in Alzheimer’s disease patients.

Dik-Lung Ma (University of Hong Kong) and colleagues made iridium(III) and rhodium(III) complexes that can both inhibit the aggregation of Ab_1-40 peptides and acts as luminescent probes for the peptides. Their iridium complex is the first example of a transition metal complex that displays a ‘switch-on’ luminescence response upon binding to Ab_1-40 peptides; the magnitude of response can be used to distinguish between the peptide’s monomeric and fibrillar forms.

Read the full Edge Article for free in Chemical Science.

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